1. Field of the Invention
The present invention relates to a thin-film magnetic head and a method for manufacturing the same, and more particularly to improvement of a thin-film magnetic head for high-density recording.
2. Description of the Related Art
In recent years, the improvement in performance of a thin-film magnetic head is demanded with the improvement in surface recording density of a hard disk device. A thin-film magnetic head is composed of a stacked structure of a write element which aims at a write operation and a read element which aims at a read operation and uses a magnetoresistance effect. Particularly, a recent GMR head is so vigorous as to exceed 150 to 200 (GB/P) in surface recording density. A GMR film is of a multilayer structure obtained by combining a plurality of layers together. There are some kinds of mechanisms generating GMR and the layer structure of a GMR film varies according the mechanisms. A spin valve film (hereinafter, referred to as an SV film) and a ferromagnetic tunnel junction film (hereinafter, referred to as a TMR film) are known as a GMR film assuming a mass production.
On the one hand, the improvement in performance of a write element is also demanded with the improvement in performance of a read element. It is necessary to realize a narrow-track structure and enhance a track density in order to enhance the recording density by a write element. As a means for realizing a narrow-track structure, there is known a method of obtaining a tentative track width by applying a photolithography method and a plating method to an upper recording member and then adjusting the track width by means of a dry etching process such as RIE, IBE or the like.
However, a technique of obtaining a tentative track width by applying a photolithography method and a plating method and then adjusting the track width by means of a dry etching process such as RIE, IBE or the like has various problems. First, since a process of obtaining a tentative track width by applying a photolithography method and a plating method and then adjusting the track width by means of a dry etching process such as RIE, IBE or the like is performed after a pole portion comprising a lower pole film, a gap film and an upper pole film is formed on a lower yoke film, due to a shadow formed by an upper pole portion in IBE or RIE an etching rate is made lower at a rise-up part of the pole portion and is made higher as being more distant from the pole portion. Due to this, the surface of the lower yoke film is made lower as being more distant from the pole portion and is made high in the vicinity of the base of the pole portion, and what is called a trim shoulder is formed. The existence of a trim shoulder causes a problem of adjacent track erase (ATE) in a write operation of data to a magnetic recording medium due to magnetic flux leaking from the trim shoulder portion.
Second, the upper pole portion is generally expanded in area at the rear part in case of being seen from the pole end face to be an air bearing surface (hereinafter, referred to as ABS) and has a flare point to be the starting point of expansion in area. The distance from the pole end face to the flare point must be set at a constant value as short as possible. The reason is that shortening the distance from the pole end face to the flare point is effective for improving the characteristic of overwrite (hereinafter, referred to as O/W) characteristic, sharpening the rise-up characteristic of a write operation, and increasing the switching speed.
However, in a technique of making the track width minute by means of IBE or RIE, shortening the flare point is limited and additionally the flare point is changed (shifted) and furthermore it is difficult to form a definite flare point.
As a means for improving the characteristics of a thin-film magnetic head, there has been known techniques disclosed in the specification of U.S. Pat. No. 6,043,959 and the specification of U.S. Pat. No. 6,259,583B1, but any of them determines the pole width by means of photolithography and, in order to enhance the recording density, must further perform a submicron process on the pole portion by means of IBE or RIE and thereby realize a narrow-track structure. However, problems as described above hang about this submicron process. The above prior arts have disclosed no means for solving the problems.